Stain release and durable press finishing using solution polymers

ABSTRACT

PROCESS FOR IMPARTING DURABLE PRESS AND SOLID RELEASE PROPERTIES TO TEXTILES CONTAINING A SIGNIFICANT MAN-MADE FIBER CONTENT, PARTICULARLY POLYESTERS, BE TREATMENT IN A BATH CONTAINING A DURABLE PRESS TEXTILE RESIN, TEXTILE RESIN CATALYST AND AN ACID SOLUTION POLYMER CHARACTERIZED BY A PH BELOW ABOUT 6.0 AND AN ACID CONTENT OF AT LEAST 20 WEIGHT PERCENT CALCULATED AS ACRYLIC ACID. LOW MOLECULAR WEIGHT, NON-FIBER-FORMING, HYDROPHILIC POLYESTERS SYNERGIZE THE ACTIVITY OF THE ACID SOLUTION POLYMER.

i d States Patent O fi 3,690,942 Patented Sept. 12, 1972 3,690,942 STAIN RELEASE AND DURABLE PRESS FINISH- ING USING SOLUTION POLYMERS Joseph K. Vandermaas, Charlotte, Larry J. Rikard, Lowell, Robert K. Dunlap, Charlotte, and James F. Lavender, Gastonia, N.C., assignors to Celanese Corporation, New York, N.Y.

N Drawing. Continuation of abandoned application Ser. No. 777,505, Nov. 20, 1968. This application Apr. 23, 1971, Ser. No. 137,067

Int. Cl. B44d 5/00 US. Cl. 117-138.8 F 5 Claims ABSTRACT OF THE DISCLOSURE Process for imparting durable press and soil release properties to textiles containing a significant man-made fiber content, particularly polyester, by treatment in a bath containing a durable press textile resin, textile resin catalyst and an acid solution polymer characterized by a pH below about 6.0 and an acid content of at least 20 weight percent calculated as acrylic acid. Low molecular weight, non-fiber-forming, hydrophilic polyesters synergize the activity of the acid solution polymer.

This application is a continuation of our application Ser. No. 777,505, filed Nov. 20, 1968, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a process for imparting soil release properties to a textile substrate. More particularly, the invention relates to a process for treating fabrics having a significant man-made fiber content to prepare durable press fabrics possessing excellent soil release properties coupled with minimal propensity for soil redeposition during repeated washing cycles.

Substantial research has been directed to the attainment of permanent press fabrics, especially durable press light weight and heavy weight fabrics constructed of 100 percent synthetic fibers and synthetic fiber/natural fiber blends, e.g. 50 to 65 percent polyester/ 35 to 50 percent cotton blends, which demonstrate superior washability in aqueous systems and the excellent stain removal properties of 100 percent natural fiber, i.e. cotton, fabrics.

Two inter-related problems appear to be responsible for the difliculties experienced in thoroughly cleaning and, as a consequence, preventing soil staining of synthetic fabrics and fabrics containing a significant man-made fiber content, particularly polyester/ cotton blends, in aqueous wash baths such as employed in home and commercial laundry washing machines. Synthetic fibers, in addition to displaying hydrophobic surface properties preventing good water penetration into fibers to remove soil therefrom, are of an oleophilic nature. Thus, the first problem involves the attraction of dirt and oily grimes to the synthetic fibers which become embedded therein and are not removed during subsequent washing cycles because of the inability of the water to thoroughly penetrate the synthetic fibers in a manner similar to the swelling of cellulosic fibers in water. Second and also due to the above-described surface properties, oily soil materials washed out of the fabric during a washing operation are continuously attracted to the surface of the fabric and become re-deposited thereon. As a result, the fabric, following only one washing, never returns to a truly clean condition and, instead, assumes a discolored, gray and/or yellow appearance which eventually renders it unfit for further use with subsequent ironing where desired tending to set in the grime. The present invention obviates the problem of soiling and staining by modifying the surface characteristics of synthetic fiber-containing fabrics, as fully disclosed hereinafter.

The prior art discloses and suggests the employment of numerous inorganic and organic materials, including mixtures thereof, as anti-soiling agents to be applied in textile finishing operations. In particular, United States Patent 3,377,249 to Marco et al. discloses the use of a particular combination of reagents to attain durable ;press, soil resistant fabric materials, said ingredients being an aminoplast textile resin, a textile resin catalyst therefor, and a synthetic acid emulsion polymer. The Marco et al. patent is predicated in large part upon the poor soil release properties obtainable according to the teachings of prior art patents, i.e. Caldwell United States Patent 3,236,685, directed to the employment of synthetic acid solution polymers as soil release agents. Therefore, it is an object of the present invention to provide durable press textile structures exhibiting excellent soil release properties. It is another object of the invention to provide a process for treating textile fabrics to render them' both durable press aid soil resistant. A further object of the invention is to provide a process for treating fabrics containing a significant man-made fiber content to prevent their discoloration during repeated water washing cycles. It is still another object of the invention to provide fabrics formed of percent synthetic fibers and natural fibers/ synthetic fiber blends containing finishes which prevent soil re-deposition during washing cycles. A specific object of the invention is to provide wash-andwear 100 percent polyester and polyester/cotton fabrics which retain their durable press attributes without discoloring in any manner during the normally expected life span of the fabric material. A further specific object is to provide improved durable press soil release formulations utilizing synthetic acid solution polymers. Another object is to provide synergistic textile finishes containing as one component thereof, such polymers. Other objects will appear obvious to those of skill in the art from the detailed description of the invention hereinafter.

THE INVENTION It has now been found that soil release and durable press characteristics can be imparted to a textile material containing a significant man-made fiber content by a process involving the application thereto of a textile resin, a resin catalyst, and a synthetic acid solution polymer having a pH within a critically-defined range.

In accordance with the invention, a process for imparting soil release and durable press properties to a textile structure is provided comprising treating said structure with a durable press finish composition curable to the thermoset state, means to cure said composition and a solution acid polymer having a pH below about 6.0 containing at least 20 weight percent acid calculated as acrylic acid.

In a preferred embodiment of the invention, there is disclosed a process for imparting soil release and durable press characteristics to a fabric containing a significant man-made fiber content, i.e. polyester/natural and/or synthetic fiber blend fabrics which comprises applying thereto a durable press aminoplast resin, an aminoplast catalyst and a solution of an ethyl acrylate/methacrylic acid co-polymer having a pH of about 4.6 to 5.7, preferably 4.6 to 5.2, and containing at least 50 Weight percent acid calculated as acrylic acid. The present invention diverges from the prior art teachings of the necessity of emulsion acid polymers in durable press-soil release finish formulations by specifying a critical pH range within which solution polymers function advantageously in durable press-soil release compositions.

In another aspect of the invention, which may also be considered as a preferred embodiment thereof, there is provided a synergistic soil release formulation which can be advantageously applied to fabrics containing a significant man-made fiber content, and especially 100 percent polyester fabrics, comprising the above-disclosed formulation, with or without durable press resin as required, in synergistic combination with a hydrophilic, low molecular weight polyester. Of course, with 100 percent polyester fabrics, the durable press textile resin need not be employed since such fabrics exhibit adequate durable press properties without additional treatment. The textile structures so treated, in addition to exhibiting superior wrinkleresistance and enhanced stain removal-soil re-deposition preventive properties, display an excellent hand.

DETAILED DESCRIPTION Durable press textile finishes, i.e. crease retaining and/ or wrinkle resistant, generally are produced by compounds capable of undergoing addition reactions, i.e. polymerizable and/or condensable organic materials, including polymers and monomers, which when applied to a textile substrate, form a film around individual fibers and undergo conversion to the thermoset state in the presence of active curing means, i.e. catalysts and/or activating energy such as by exposure to radiation. Hence, the terms textile resin, compound capable of imparting a durable press finish and the like, as used herein are intended to encompass any material regardless of particular chemical classification as naturally-occurring, synthetic, polymer, monomer and the like, as long as it is condensable and/ or polymerizable into a thermoset addition compound capable of imparting wash and wear characteristics to fabrics, and particularly fabrics containing a significant polyester content. As an example of one class of durable press finish compositions widely used today, there may be mentioned the aminoplast resins. The aminoplast resins, of which numerous examples are stated hereinafter, form self-addition polymers and/or condense with, for example cellulose molecules, under curing conditions of about 125 to 250 degrees centigrade to form thermoset resins imparting durable press and/or wrinkle resistant characteristics to a textile substrate. Aminoplast resins operable in the present invention include, among others, the following: the urea formaldehydes, e.g., propylene urea formaldehyde, dimethylol urea formaldehyde, etc.; melamine formaldehydes, e.g. tetramethylol melamines, pentamethylol melamines, etc.; ethylene ureas, e.g. dimethylol ethylene urea, dihydroxy dimethylol ethylene urea and dialkoxy substituted derivatives thereof such as dimethoxy dimethylol cyclo ethylene urea, ethylene urea formaldehyde, hydroxy ethylene urea formaldehyde, etc., carbamates, e.g., alkyl carbamate formaldehydes, etc.; formaldehyde-acrolein condensation products; formaldehyde-acetone condensation products; alkylol amides, e.g. methylol formamide, methylol acetamide, etc.; acrylamide, e.g. N-methylol acrylamide, N-methylol methacrylamide, N-methyl-methylolacrylamide, N-methylol methylene-bis (acrylamide), methylene-bis(N-methylol acrylamide), etc. haloethylene acrylamide; diureas, e.g. trimethylol acetylene diurea, tetramethylol acetylene diurea, etc.; triazones, e.g., dimethylol N-ethyl triazone, N-N-ethylene-bis dimethylol triazone, halotriazones, etc.; haloacetamides, e.g. N-meth ylol-N-methyl-chloracetamide, etc.; urons, e.g. dimethylol uron, dihydroxy dimethylol uron, etc. and the like. Mixtures of aminoplast textile resins are also within the scope of the present invention as well as the aforementioned compounds carrying additional inert and/ or active substitution groups.

The amount of durable press finish composition applied to the fabric is not critical to the present invention and may vary widely but will generally be used in the same concentration normally employed in conventional finish operations. Therefore, the durable press finish formulation applied to the fabric could be in the range of about 1 to percent based on the dry weight of the fabric and usually will be in the range of about 4 to 10 percent. To

assure application of adequate aminoplast levels onto the fabric, a textile treating pad bath should contain, by weight, about 5 to 30 percent resin solids and preferably about 7 to 14 percent.

The particular curing means employed in the invention will depend upon the specific durable press composition present and will most often consist of an organic or inorganic catalytic material, numerous examples of which are disclosed in the prior art. For example, with the abovestated aminoplast resins, the catalyst will either be of a basic and/or acid nature depending upon the particular type of catalysis required for condensation, i.e. if the resin has a functional group reactable under acidic conditions, an acid catalyst is used and vice-versa. At times both acid and basic catalysts, one of which will be of a latent character, are employed. As examples of catalysts operable within the scope of the invention, which generally are also employed to activate the identical comparable aminoplast resin for reaction with cellulosic hydroxyl groups, there may be mentioned as acid catalysts certain inorganic metallic salts such as zinc nitrate and magnesium chloride and organic amino salts, i.e. monoethanolamine hydrochloride and 2-amino-Z-methyl-propanol nitrate; basic catalysts such as the alkali metal carbonates, silicates and phosphates, i.e. sodium or potassium bicarbonate, carbonate, silicate and/or phosphate and quaternary ammonium compounds such as the hydroxides and carbonates, i.e. lauryl trimethyl ammonium carbonate. Latent catalytic materials, as is well known, may be activated by particular environmental conditions of curing, i.e. temperature, pH and the like, such as decomposition of alkali metal carbonates into the oxide at about degrees centigrade and/or by additional chemical compounds such as the decomposition of potassium sulfite in the presence of formaldehyde into the corresponding hydroxide and the like. The above catalytic salts may be employed in widely varying concentrations in suitable pad baths depending upon degree of activity, percentage resin present and the like. Preferably such salts will be present in amounts ranging from about 5 to 40 percent by weight based on resin weight and preferably about 15 to 25 percent.

The compositions of the invention are particularly suitable for application to any type substrate containing linear polyester fibers to improve the washing characteristics thereof. Preferably, the substrate is a textile material, including staple fibers, monoand/or multifilaments, yarns, including fibrillated materials, fabrics, i.e. knitted, woven and non-Wovens and textile end-products constructed therefrom, and is percent polyester or contains a significant amount of polyester. The invention is particularly directed to woven fabrics and end-products constructed therefrom formed of polyester/cellulosic fiber, i.e. polyester/cotton yarn blends. Further, the invention is equally applicable to other man-made and synthetic fibers (the former terms being used interchangeably herein) and intermediate and end-products fabricated therefrom, i.e. acetate, including both secondary and triacetate, regenerated cellulose, polyamide, polyacrylonitrile, polyurethane and polyvinyl halides. In a preferred application of the invention, the finish formulation is applied to fabrics constructed of a significant amount of polyester also containing a second man-made fiber in addition to cotton. By the designation significant amount is meant a textile substrate containing at least 35 percent and preferably about 50 to 80 percent man-made fiber content, e.g. polyester.

The soil release polymer of the present invention, in contradistinction to prior art requirements of emulsion polymers in a durable press-soil release formulation, is a solution polymer having a pH within a defined range coupled with a minimal weight percentage of acid calculated as acrylic acid. With these restrictions in mind, any of a large number of organic polymers and copolymers may be employed. The essential characteristics required is that the acid polymer is a solution polymer; that is, the

polymer is dissolved in a solvent medium instead of being uniformly suspended throughout a non-miscible solvent such as in the case of polymeric latexes and other types of oil in water and water in oil emulsions, and, secondly, that the acid solution polymer either inherently exhibits a pH within the required range or its pH can be adjusted to be within said range by addition of acid or base without destroying solubility and altering minimal acid values. The solvent medium may vary depending upon the particular acid polymer and its compatibility with other bath ingredients, particularly the durable press finish composition. However, by solution polymer will most often be meant a polymer sufficiently water soluble to enable employment of an aqueouse finish bath. Of course, the solvent could be of an organic nature, i.e. acetone, benzene and the like or a combination of 2 or more miscible solvents.

Polymers derived from solution polymerization methods are preferred over solubilized emulsion polymerization polymers due to their greater purity and relative lack of adherred contaminants, especially emulsifying agents, which affect final fabric properties such as uniformity of dye uptake, static properties, hand and the like. Also solution polymers are generally of lower molecular weight which aids fiber penetration and soil release polymer compatibility in the pad bath.

The acid solution polymer may be selected from homopolymers, usually partially neutralized, or copolymers of polymerizable acids having a carbon atom to acid group ratio of 2:1 to 30:1. Although the most preferred soil release polymers are copolymers of acrylic and substituted acrylic acids, other polymerizable acids falling within the above ratio and forming a polymer having an acid content of at least 20 weight percent calculated as acrylic acid may be employed in copolymers formed from two or more monomers. As examples of suitable monomeric acids, in addition to the preferred acrylic and methacrylic acids, which may be used within the scope of the invention, there may be mentioned polymerizable sulfonic and phosphoric acids, other low molecular weight monomeric carboxylic acids, i.e. butanoic and pentanoic acids, and ethylenically unsaturated dicarboxylic acids containing 4 to '8 carbon atoms, such as fumaric acid, maleic acid, itaconic acid, citraconic acid and the like, and the anhydrides of such acids convertible to free carboxyl groups in solutions. Moreover, water soluble homopolymers of many of the above-mentioned acids may be prepared and the pH thereof suitably adjusted to within the defined range, i.e. acrylic acid, itaconic acid and the like. Additionally, salts of the acid polymer-s, especially from neutralization occurring in the regulation of pH, are within the scope of the invention. Monomers interpolymerizable with the monomeric acid are those which form film-forming solution polymers therewith. As examples of such copolymerizable monomers, there may be mentioned vinyl alkyl ethers such as vinyl methyl or ethyl ether, methyl vinyl ketone, styrene, alkyl half esters of the dicarboxylic acids such as methyl acid maleate, the alkyl esters of the carboxylic acids such as ethyl acrylate, methyl acrylate, propyl acrylate, the corresponding methacrylates and other polymerizable vinyl or vinylidene compounds having at least one CH =C group such as vinyl acetate and the vinyl halides. Further, two or more of the above acid monomers and/or copolymerizable monomers may be employed to prepare acid solution polymers aplicable to the invention. Preferably, the acid solution polymer is an acrylic or methacrylic acid copolymer in which the comonomer is an acrylate formed from an alcohol containing 1 to 3 carbon atoms and, most preferably the acid solution polymer will be a methacrylic acid/ethyl acrylate copolymer. The polymer will generally have a molecular weight above 500 and usually above 3,000.

The above polymers may be prepared according to polymerizable procedures well known in the art. Generally, either mass or solution polymerization techniques are employed although suspension polymerization is applicable. With mass polymerization, the polymer is usually obtained as a solid which is subsequently ground into small particles prior to solution. In solution polymerization, the monomeric ingredients along with activating means if required are dissolved in a suitable solvent, with polymerization occurring autogenously or by activation by heat, pressure, catalysts, radiation and the like. Solvents which may be used are benzene, ethyl acetate, methyl acetate, ethanol, butanol, and most preferably, water. The catalytic means, where required, will be tailored to the particular type of polymerization and monomers involved. As examples, there may be mentioned heat, pressure, ultra-violent radiation, free radical catalysts such as benzoyl peroxide and other types of polymerizationinitiators such as the halogenated ionic initiators.

As disclosed hereinbefore, the acid solution polymer to impart good soil release ability, will have a pH below about 6.0, preferably below about 5.7 and most preferably about 4.6 to 5.2 with an acid content calculated as acrylic acid of at least 20 weight percent. Out of the foregoing polymeric materials, the more preferred are ethyl acrylate/methacrylic acid copolymers containing over 50 percent by weight methacrylic acid and most preferably, 75 to percent acid calculated as acrylic acid, said polymers pH being suitably adjusted to, most preferably, a pH of about 5.0. The use of such copolymers containing high weight percentages of acid calculated as acrylic acid is again contrary to the relevant prior art. However, said polymers do not display their superior soil release properties, in combination with the durable press finish formulation, unless exhibiting a pH as stated herein. This is even more surprising since the initial pH of the acid solution polymer is what is critical irrespective of the addition of other normally acceptable finishing agents such as surface active agents, fabric softening agents and the like to the ultimate finish bath.

The soil release resins, as with the durable press finish compositions, may be employed in a wide range of concentrations. Even though relatively small amounts of acid polymer, i.e. of the order of less than 1.0 percent, i.e. 0.25 percent by weight in the finish bath, will impart a low level of soil release properties to textile structures, a preferred range of acid polymer solids in the bath would be about 20 to 60 and most preferably about 30 to 40 weight percent to apply, based on dry fabric weight about 1 to 3 weight percent acid polymer solids, preferably about 1.5 to 2. weight percent, to the substrate. The polymeric solution will most likely contain. about 20 to 60 percent solids, the amount added to the bath being determined by the final bath volume, percent solids in the polymer solution, percent add-on desired and the like, all of which are within the skill of those in the art. The finish bath containing the durable press composition, catalyst, and acid solution polymer and, optionally, other auxilliary finish bath compositions such as the synergistic low molecular weight polyester as disclosed hereinafter, may be applied to the textile substrates in any of a number of ways, i.e. dipping, spraying, padding and the like.

The durable press composition, catalyst when used to cure said composition and acid polymer may be applied to the textile structure in nearly any order of ingredient application and the physical properties of the structure are improved. However, it is preferred for excellent enh ancement of soil release properties that the permanent press composition be cured in the presence of the acid polymer. :In such instance, all ingredients should be applied simultaneously or in any order of application as long as curing does not occur until after treatment with the acid polymer solution. Likewise, the invention is equally applicable for precured, e.g. light weight garment, and delay-cured, e.g. heavy weight garment, fabric finishing. With the latter, latent curing agents are generally employed.

For curing, heat sensitive catalytic materials are gen erally employed with the fabrics being heated to about 320 to 400 F. for about seconds to 2 minutes for precured and about 10 to minutes for delay-cured garments. The curing medium may be any substance inert to both the fabric and finish formulation and capable of supporting the required temperatures, i.e. hot air, steam, organic vapors and the like. Of course, pressing to set in creases where desired is accomplished prior to final curing.

In a very preferred aspect of the invention, a hydrophilic polyester, i.e. low molecular weight, non-fiberforming polyester containing a preferential ratio of hydrophilic/hydrophobic groups, is incorporated into the textile resin finish bath for enhanced soil release, and ap parently synergistic, soil release properties. The polyestersynthetic acid solution polymer combination together with the textile resin and catalyst is particularly suitable for treating fabrics constructed of a significant percent of man-made fibers, especially fabrics containing a significant amount of linear polyester with the balance of the fabric content being one or more other synthetic fibers. The results achieved with respect to soil removed and lack of re-disposition through repeated launderings have heretofore been unobtainable with 100 percent polyester garments stained with oily and oleophilic particulate soiling materials. Of course, the durable press resin is not required with the soil release treatment of 100 percent polyester substrates.

As variants within the above generic description of the synergistic textile treating formulation containing low molecular weight polyester, there may be mentioned the use of additives disclosed in the art which further enhance the degree of soil resistance of such polyester, i.e. starch or cellulose derivatives as disclosed in copending commonly assigned application Ser. No. 671,605, filed Sept. 29, 1967 of Dunlap, now Patent No. 3,512,920, incorporated herein by reference.

The low molecular weight alkylene glycol/polyalkylene glycol terephthalic acid esters are most suitable in this embodiment of the present invention and may be described as copolymers of terephthalic acid, a lower molecular weight alkylene glycol, and a polyalkylene glycol. Generally the copolymer will be a random copolymer, although a partial block copolymer may result under certain reaction conditions.

The low molecular weight terephthalate polymers may be prepared by esterification of appropriate glycols with free terephthalic acid or by ester interchange with lower molecular weight monoalkyl and dialkyl terephthalates. More specifically, the terephthalates which may be employed in preparing the polymers used in the present invention are those having a total of from about 1 to about 7 carbon atoms, and preferably from about 1 to about 4 carbon atoms, in the alkyl chain, or in the case of the diesters, in each alkyl chain. Examples of suitable esters are monoethyl terephthalate, dimethyl terephthalate, methyl ethyl terephthalate, and diethyl terephthalate.

Suitable alkylene glycols are the lower molecular weight alkylene glycols, e.g. alkylene glycols having a total of from about 1 to about carbon atoms, and preferably from about 2 to about 6 carbon atoms. Illustrative alkylene glycols include ethylene glycol, 1,2-propane diol, 1,3-propane diol, butylene glycol, and mixtures thereof.

Similarly, the polyalkylene glycols employed in the present invention include the glycols having from about 2 to about 10 carbon atoms, and preferably from about 2 to about 4 carbon atoms per repeating unit. Such polyalkylene glycols include polyethylene glycol, polybutylene glycol, and copolymers and mixtures thereof. Desirably, the polyalkylene glycol employed will have an average molecular weight of from about 200 to about 20,000 and even more preferably from about 1,000 to about 5,000. From the standpoint of ease of preparation and commercial availability, those polyalkylene glycols are preferred which are prepared from alkylene glycols having hydroxyl groups on adjacent carbon atoms.

Commonly, the lower molecular weight polyesters utilized in the present invention are prepared by heating a mixture of the aforesaid reactants in the presence of a catalyst such as antimony trioxide, and distilling off the volatile by-products to obtain the polymeric residue. The reaction should be stopped prior to the formation of a polymer which will be fiber-forming. Desirably, the relative viscosity of the polymer (the viscosity of a one percent solution in o-chlor-phenol at 25 degree centigrade divided by the viscosity of the solvent) will be from about 1.1 to about 2.0, and more preferably, will be from about 1.2 to about 1.5.

Preferably, the polyalkylene glycol and alkylene glycol are combined in a molar ratio of from about 1:1 to about 1:10, and even more preferably in the ratio of from about 1:2.5 to about 1:5. While ratios outside of the broader range given above will yield products which are still somewhat suitable in the present invention, it appears that the hydrophobic/hydrophilic balance obtained in products resulting from a combination in the above broader ratio is most desirable for the purposes of the present invention; the hydrophilic properties are imparted by the ether-oxygen atoms in the polyalkylene glycol chains.

In the above reaction, a stoichiometric amount of the dialkyl terephthalate, based on the total mols of alkylene glycol and polyalkylene glycol is employed.

Preferred lower molecular weight terephthalic acid polyesters are those prepared by reacting polyethylene glycol, ethylene glycol and dimethyl terephthalate utilizing the preferred molar ratios, molecular weights and relative viscosities given above.

While the foregoing method is commonly utilized in preparing the present non-fiber-forming polyesters, it will be understood by one skilled in the art that other methods may be employed in preparing these materials for use in the present invention. Similarly, other equivalent polyesters containing hydrophilic groups may be employed, e.g. wherein the terephthalic moieties are replaced in whole or in part by adipic groups, and the like.

As stated earlier, the low molecular weight polyester may be incorporated into the textile resin pad bath or applied along with one or more of the other ingredients in a separate application which usually would also be in the form of a pad bath. Of course, other methods of treatment as detailed above would be applicable for applying the polyester component. In any event, as also previously explained, all of the ingredients should be applied prior to textile resin Curing for maximum soil resistant effect. Concentration of the polyester in the particular treating medium should be adjusted to afford the desired amount pick-up on the fabric, usually about 1.5 to 3.0 weight percent solids based on dry fabric weight.

The following examples are presented to exemplify the principles of the invention and are not intended to limit the scope thereof as defined by the appended claims. All percentages are by weight unless otherwise indicated.

Example I This example illustrates the poor results with respect to stain release in accordance with prior art teachings relating to the employment of solution acid copolymers wherein pH and/or free acid concentration i.e. inclusion of cross-linking agents, are not regulated.

Samples of polyester/cotton (65/35) are treated with a pad bath containing 11 percent N-methylol acrylamide; 2.1 percent zinc nitrate, 1 percent Dupanol WAQE, a surfactant sold by E. I. du Pont de Nemours and Company, 81.9 percent water and 4 percent of an aqueous solution which provides, based on total formulation, 0.25

percent polyacrylic acid and 0.0075 percent pentaerythritol. Similarly, other samples of the identical fabric were treated in pad baths in which the polyacrylic acidpentaerythritol was replaced with aqueous solutions providing, based on total pad bath, (A) 0.25 percent solution copolymer of ethyacrylate/acrylic acid (70:30) and 0.0075 percent pentaerythritol and (B) 4 percent polyacrylic acid and 0.1 percent pentaerythritol.

The fabrics were dried at 120 degrees centigrade; subjected to an irradiation dosage of 1 megarad, one rad being the amount of energy resulting in absorption of one hundred ergs per gram of absorbing material, and heated in an oven at 150 degrees centigrade for about 15 minutes. The cured fabrics were then neutralized by 10 fabric weight, eg if 100 grams of fabric after padding Weighs 175 grams, the wet pickup is 75%), the fabrics are dried at 200 F. and cured at 340 F. (2 minutes for the lightweight fabrics and 10 minutes for the heavyweight fabrics.)

'Each fabric sample is then scoured and bleached and divided into two test portions, the first being washed one time in a Kenmore automatic washer with Tide detergent before staining while the second is subjected to five washings before being stained. Each sample is then washed one additional time prior to being rated for stain removal efiiciency against standards as described in Example I. Wash water temperature is about 140 F. in all instances. The results are tabulated below in Table II.

TABLE II Lightweight 50/50 Heavyweight 50/50 polyester/cotton polyester/cotton Sample Soil release agent in pad bath 1 prewash 5 prewashes 1 prewash 5 prcwashes 1 Acid solution copolymer of ethyiacrylatelm t a yl 4 4 4 4 2 Acid emulsion copolymer of ethyiacrylate/ et ac y c ac d" 3 4 1 2 Control agent. Without soil release 1 1 1 1 scouring with a solution of Tide detergent at 140 F., rinsed and dried.

Samples of all of the resulting fabrics were stained with mineral oil and laundered in a Kenmore automatic washer using a normal cycle with one cup of Tide detergent and a water temperature of 120 F. Other fabric samples of each set were washed five times, and dried before being stained with mineral oil and subjected to one further wash under the wash conditions set forth above. After the designated number of washes, each fabric was examined and the residual oil stain compared with a set of standards having numerical ratings from 1.0 to 5.0 with a 5.0 rating being complete stain removal, a 1.0 rating signifying virtually no stain removal and a 3.0 rating being acceptable. The following Table I lists the soil release ratings for each of the fabrics after the designated This example shows that the employment of a textile resin and the solution polymers as set forth above do not impart significant soil release characteristics (without selective characteristic control in accordance with this invention).

Example II Samples of light weight and heavy weight polyester/ cotton (50/ 50) fabrics are stained with graphite in transmission oil and washed according to the procedure described herein after following treatment in a pad bath containing 200 g./l. Permafresh 113 B permanent press resin (a lower-alkoxy substituted dihydroxy dimethylol ethylene urea available from Sun Chemical Corporation), 40 g./l. zinc nitrate catalyst, g./l. Triton X-200, a surface active agent available from Rohm and Haas and 300 g./l. of a water soluble acid copolymer of ethyl acrylate and methacrylic acid (:80) having a pH of 4.7. Similarly, fabric samples are treated in pad baths containing, substituted for the acid solution copolymer, 300 g./l. of an ethyl acrylate/methacrylic acid emulsion copolymer (60:40). Following treatment in the pad bath to give a 75 percent wet pickup (amount of finish absorbed by the fabric during padding, calculated as percentage of the dry The solution polymer employed in the above example has a pH of 4.7 while the emulsion polymer exhibits a pH of about 2.75. When the above test is repeated with either polyacrylic acid or the identical acid solution copolymer partially neutralized so as to have a relatively high pH, i.e. about 7.0, it is unexpectedly found that the stain release ratings of all fabrics, particularly the heavy weight, delay-cured materials are considerably lower.

Example III Realizing from the results of the test of Example II that at least some acid solution polymers, apparently depending upon pH, display excellent soil release properties when applied to fabrics containing a significant man-made fiber content, testing is conducted to pin-point the effective pH range for said acid solution copolymers. To accomplish this, Example II is repeated, limited to heavyweight polyester/cotton 65/35 fabrics with water-soluble ethyl acrylate/methacrylic acid copolymer (20/ at various pHs ranging from 4.6 to 7.5. The 4.6 pH material consists of a 24.5 percent aqueous solution of the copolymer. To prepare the higher pH materials, a 50 percent by weight solution of potassium hydroxide is added until the desired pH is reached. The results are tabulated in Table III along with the pHs of the respective pad baths. The staining material is a suspension of graphite in transmission oil.

It is apparent from Table III, other variables remaining constant, that pH determines the soil release efiiciency of a particular acid solution copolymer and a comparison with the previous example will indicate that solution polymers may equal or improve upon emulsion polymer results when prepared and utilized in accordance with this invention. Within the confines of the present experiment, the pH of the pad bath is of secondary importance, i.e. addition of other acids such as strong inorganic acids to change pad bath pH doesnt improve soil release. Of course, the pad bath should not contain any material which would appreciably neutralize the soil release acid, i.e. should contain only normally acceptabe pad bath ingredients.

The critical pH for the copolymer is about 6.0 with copolymers having higher pHs showing unacceptable soil release ability when applied to fabrics containing synthetic, particularly linear polyester fibers. Optimum results are realized with a particular polymer exhibiting a pH within the range of about 4.6-5.2 or more precisely about 5.0.

The underlying reasons accounting for the superior soil release effectiveness within the specified pH range i.e. below 6.0 or more particularly between about 4.6 and 5.7 have not been determined Within any degree of certainty. However, it is postulated that a number of interrelated factors are at work such as physical and chemical compatibility, particularly miscibility with permanent press resin formulations, treatment bath stability within certain pH ranges, number of available carboxylic groups on the acid solution copolymer, and the like. The salient feature of this invention lies in the recognition that other factors and parameters remaining unchanged, soil release elfectiveness of an acid solution copolymer is remarkedly enhanced as a result of its pH regulation. Of interest is the teaching of Example I that unneutralized polyacrylic acid of pH 2.8, displaying a higher availability of dangling carboxylic groups and an acid value much higher than the copolymer, is less effective than the copolymers as a soil release agent on polyester/cotton blends.

Example IV This example demonstrates the superior results realized when the acid solution polymer is employed in combination with a textile resin as opposed to being used alone for fabric treatment. Example III is repeated with only the copolymer in the pad bath, the results being set forth in Table IV.

TABLE IV Soil release rating 1 prewash prewashes Copolymer pH:

Example V As discussed above, one aspect of the present invention relates to the use of a low molecular weight, nonfiber-forming, hydrophilic polyester to synergize the soil release ability of acid solution polymers. Although a number of soil release finishes, including the solution polymers of the present invention, yield an acceptable level of performance, i.e. a rating of 3, with 100 percent polyester garments, there is especially a need for better soil release finishes for such fabrics. In particular, it is extremely difficult to effectively remove olephilic staining materials from the hydrophobic surfaces of 100 percent polyester fabrics which, as would be expected, display a higher relative affinity for olephilic staining materials than the polyester/cotton blends. Additionally, there is a lower relative water penetration into the 100 percent man-made fabric, another important factor for consideration. Obviously, it is quite unexpected and surprising to find the enhanced soil release resulting from the use of the watersoluble copolymer in combination with the low molecular weight polyester having a higher relative hydrophilic rating, or preferential atfinity for an aqueous system, when disposed at an oil/ water interface.

The testing procedure as outlined in Example II is repeated using a 100 percent polyester fabric and a pad bath containing 15 g./l. Triton X-200 and 300 g./l. of a 24.5 percent by weight solution of ethyl acrylate/methacrylate acid (20/80) solution copolymer having a pH of 4.7. Likewise, the experiment is repeated substituting for the solution copolymer (A) 280 g./l. Cirrasol PT (a polyester having a relative viscosity of 1.25 prepared by the reaction of polyethylene glycol of 1540 molecular weight and ethylene glycol in a molar ratio of 1:25 with a stoichiometric amount of dimethyl terephthalate) and (B) separate formulations consisting of 280 g./l. Cirrasol PT and 300 g./l. solution copolymer of ethyl acrylate/ methacrylic acid (20/80), said formulations being consecutively padded into the fabric. The test fabrics are stained with a suspension of graphite in transmission oil. Due to the percent polyester content, the fabrics are subjected to curing conditions of 385 F. for 30 seconds. In all instances, i.e., 1 and 5 prewashes, the soil release rating with the combination treatment (B) is substantially higher than that obtainable with either the solution copolymer or Cirrasol PT in the absence of the other. In addition, while the copolymer gives an acceptable rating, about 3 average value, the combination yields soil-release ratings approaching 5.0 with an average value of about 4.0

Then enhancement of soil release on polyester/cotton blends through perusal of the formulation including low molecular weight polyester is not as pronounced as with 100 percent polyester materials but still appreciable and indicative of a general synergistic effect which can be used to advantage on nearly all types of synthetic fiber/ natural fiber blends. In such instance, a durable press resin should be included within the treatment, and preferably, subjected to curing conditions following application of all ingredients.

Numerous modifications within the scope of the invention will appear obvious to those of skill in the art. For example, other soil release agents in addition to the abovedescribed polyesters may be added to the treatment bath, i.e. the acid emulsion polymers of the prior art.

What is claimed is:

1. A process for imparting soil release and permanent press characteristics to a textile material comprised of at least 35 percent of synthetic fiber comprising the steps of sequentially:

(a) passing said textile material through a bath comprised of 1) from about 5 to about 30 percent of an aminoplast textile resin,

(2) from about 5 to about 40 percent of a textile resin catalyst, and

(3) from about 20 to about 60 percent of a synthetic acid solution polymer having a pH within the range of about 4.7 to about 6.0 which polymer is comprised of at least 20 weight percent acid calculated as acrylic acid; and

(b) curing the textile material;

wherein, prior to the time said textile material is cured, there is also applied to said textile material a hydrophilic, low molecular weight polyester, said low molecular weight polyester being produced by copolymerizing a mixture of a terephthalate, an alkylene glycol, and a polyalkylene glycol, wherein:

(c) said terephthalate is selected from the group consisting of terephthalic acid and the monoand dial- -kyl esters of terephthalic acid wherein said esters have from 1 to 7 carbon atoms in each alkyl group;

(d) said alkylene glycol has from 1 to about 20 carbon atoms;

(c) said polyalkylene glycol has from 2 to about 10 carbon atoms per repeating unit and an average molecular weight of from about 200 to about 20,000;

(f) from about 1 to about 10 parts of said alkylene glycol are present in said mixture for every part of polyalkylene glycol;

(g) said mixture is copolymerized by heating it in the 13 presence of a catalyst, distilling oil the volatile byproducts and stopping the copolymerization reaction when a polymer with a relative viscosity of from about 1.1 to about 2.0 is produced; and

(h) sufficient low molecular weight polyester is applied so that said textile material picks up from about 1.5 to about 3 percent of said polyester.

2. The process of claim 1, wherein:

(a) the pH of said synthetic acid solution polymer is from about 4.6 to about 5.7, and said acid is a copolymer of an acrylic acid and an acrylic ester;

(b) said synthetic fiber is selected from the group consisting of polyester fiber, polyamide fiber, polyacrylonitrile fiber, acetate fiber, polyurethane fiber, and polyvinyl halide fiber;

(c) said textile material is cured by heating it at a temperature of from about 320 to about 400 degrees centigrade for from about 10 seconds to about 15 minutes;

(d) said terephthalate is a dialkyl ester of terephthalic acid having from 1 to about 4 carbon atoms in each alkyl chain;

(e) said polyalkylene glycol has from 2 to about 4 carbon atoms per repeating unit and an average molecular weight of from about 1000 to abou 5000;

(13) from about 2.5 to about 5 parts of said alkylene glycol are present in said mixture for every part of polyalkylene glycol in said mixture.

3. The process of claim 2, wherein:

(a) said acid is a copolymer of methacrylic acid and ethyl acrylate,

(b) said bath is comprised of from about 7 to about 14 percent of an aminoplast textile resin, from about 14 15 to about 25 percent of textile resin catalyst, and from about to about percent of synthetic acid solution polymer; and

(c) a stoichiometric amount of said dialkyl ester is present in said mixture.

4. The process of claim 3, wherein:

(a) said synthetic fiber is polyester fiber;

(b) said terephthalate is dimethyl terephthalate, said alkylene glycol is ethylene glycol, and said polyalkylene glycol is polyethylene glycol; and

(c) said copolymerization reaction is stopped when a polymer with a relative viscosity of from about 1.2 to about 1.5 is produced.

5. The process of claim 4, wherein:

(a) the pH of said synthetic acid solution polymer is from about 4.6 to about 5.2, and said polymer is comprised of at least weight percent acid calculated as acrylic acid, and

(b) said textile material is comprised of from about 50 to about percent of polyester fiber.

References Cited UNITED STATES PATENTS 3,377,249 4/1968 Marco 8-115.6 3,236,685 2/1966 Caldwell et al. 1l7138.8

MURRAY KATZ, Primary Examiner T. G. DAVIS, Assistant Examiner U.S. C1. X.R.

l17-l38.8 N, 138:8 UA, 138.8 D, 139.4, 139.5 A, 143 A, 145 

